In conventional hard disk drive (HDD) systems, the recording media is coated with a ferromagnetic film that contains tiny magnetic grains. This ferromagnetic film acts as the recording layer for the media. In longitudinal recording media, the magnetization easy direction of the grains of the recording layer is in the plane of the film. In perpendicular recording media, the magnetization easy direction of the grains of the recording layer is perpendicular to the plane of the film. Perpendicular recording media offers the advantage of increased storage density over longitudinal recording media. Perpendicular recording is predicted to allow storage densities of up to around one Tbit/sq. inch (1000 Gbit/sq. inch) or higher.
The ferromagnetic material iron platinum (FePt) is a material that is of great interest in the field of magnetic data storage, especially as the recording layer in hard disk drive applications, because of its relatively high magnetocrystalline anisotropy. FePt is an example of crystalline material with the L10 structure. An ideal L10 single crystal is based on a face centered cubic material (fcc) but consists of an equal number of two kinds of atoms, in this case Fe and Pt. Along the atomic ordering direction, or c-axis, each atomic plane consists of one kind of atom and the adjacent planes consist of the other kind of atom. Usually, the distance between the adjacent atomic planes along the ordering direction [001] is slightly shorter than the other two orthogonal <100> directions.
When used as a thin film perpendicular media, the c-axis of the FePt L10 is grown perpendicular to the plane of the film. If the FePt thin film is deposited at room temperature, however, it is usually not sufficiently atomically ordered. That is, if deposited at room temperature, a large number of the Fe and Pt atoms do not assume the L10 structure. Sufficient ordering for the L10 structure can usually only be achieved when the FePt thin film is deposited at an elevated temperature (about 550° C. or above) or when a high temperature post annealing process is used. Because aluminum (Al) is often used in the hard disk substrate, such high fabrication temperatures often result in damage to the recording media.